1. Field of the Invention
This invention relates to hydrolytically stable alkoxylated derivatives of 2-hydroxyalkyl substituted aminimides.
2. Description of the Prior Art
Aminimide chemistry has been extensively studied in recent years. The most comprehensive survey of this field of technology can be found in Chemical Reviews Vol. 73, p. 255 (1973).
One of the classes disclosed in the literature is the hydroxyalkylaminimides, which is distinctive in having a hydroxyalkyl group on the tertiary nitrogen. This class of compounds is depicted by Formula I. ##STR1##
Compounds of the foregoing type are convenient starting materials for the compounds of this invention, and are most easily prepared by the method described in U.S. Pat. No. 3,485,806.
During the early investigations of aminimide technology, the aminimide corresponding to Formula I were thought to be hydrolytically stable. Those aminimides having no hydroxy group in the 2- position on the alkyl group attached to the nitrogen (Formula II, where R is alkyl) were found experimentally to be stable to base. ##STR2## As reported in Chemical Reviews Vol. 73 p. 267 (1973), aminimides of Formula II where R is alkyl and A is phenyl were unaffected by boiling with 6 N sodium hydroxide for 24 hours.
It had been assumed that the hydroxyalkylaminimides of Formula I are equally as resistant to base hydrolysis. Thus, the literature has not pointed out any tendency of hydroxyalkylaminimides toward hydrolytic instability. This assumption was based on theory and also on preliminary performance data.
There was no theoretical basis to expect the hydroxalkyl aminimide of Formula I to be less resistant to base attack than the trialkylaminimide of Formula II. The hydroxy group would not be expected to affect the electrophilicity of the carbonyl carbon. Nor would one expect that removal of a proton from the hydroxy group by base would cause degradation of the aminimide moiety. Further, performance data indicated that hydroxyalkyl aminimides of Formula I (A = alkyl with carbon chain of 11, 13, 15 or 17 carbon atoms, R.sup.1 and R.sup.2 = methyl, R.sup.4 = H, R.sup.5 = methyl) were useful surfactants and exhibited no apparent degradation in 23% aqueous sodium hydroxide.
Based on the accepted theoretical considerations of aminimide chemistry and in light of the published performance data, it had been assumed that the hydroxyalkylaminimides of Formula I, while having surfactant properties different from those of the trialkylaminimides of Formula II, had hydrolytic stability equal to that of the trialkylaminides.
Contrary to the early preliminary observations, it has recently been found that the hydroxyalkylaminimides of Formula I do suffer from hydrolytic degradation with time. For example, the compound having the structure of Formula III; ##STR3## was found to be stable as a 5% aqueous solution for at least 63 days, but suffered 34% decomposition at room temperature after 230 days. Many potential applications for aminimides depend on hydrolytic stability over an extended period of time; wide commercial use of aminimides as surfactants requires a shelf life (stability) of at least 2 years. Table I shows the data for the decomposition of the compound of Formula III at reflux at a 5% concentration in IN NaOH.
Table I ______________________________________ Hours at Percent reflux decomposition ______________________________________ 2 26.3 3 29.0 4 39.5 5 47.4 6 55.3 24 94.7 ______________________________________
Table Ia shows data for the decomposition of the compound of Formula III as a 5% dispersion in distilled water at 180.degree. F.
Table Ia ______________________________________ Hours at Percent 180.degree. decomposition ______________________________________ 10 14 16 27 24 47 32 68 ______________________________________
Table II shows the decomposition of the Compound of Formula III at room temperature at a 5% concentration in NaOH.
Table II ______________________________________ Days % decomposition ______________________________________ 13 2.6 26 5.3 33 7.9 40 18.4 ______________________________________
The mechanism of this hydrolytic degradation is unknown, and therefore the stabilization of hydroxyalkylaminimides to hydrolysis presented difficulty. Because of the resonance possibilities in aminimides, there are three possible sites for reaction when electrophillic reactants are used. These points of attack are the carbonyl oxygen in the enol form (A), the negatively charged nitrogen of the aminimide (B), and the alkoxide ion formed by reaction with base (C). ##STR4##
Reaction at either site (A) or (B) would destroy the basic aminimide structure and would also destroy the inner salt configuration thought to be responsible for the properties of aminimides.